This invention relates to devices for propelling a projectile, and more particularly, to a small and lightweight device for releasing a compressed gas from a compressed gas capsule to propel a projectile. The invention also encompasses methods for releasing compressed gas from a compressed gas capsule for propelling a projectile.
Numerous devices and mechanisms have been devised for propelling a projectile toward a target. Firearms, for example, use the sudden release of pyrotechnic gasses from a gunpowder or other pyrotechnic charge to propel a bullet. Due to government control and other constraints placed upon firearms, however, other means of providing a projectile propulsion force have been developed. Such non-pyrotechnic devices include devices for releasing compressed gas such as CO.sub.2 from a compressed or liquified gas capsule to propel a projectile.
Some compressed gas cartridge weapons are adapted to utilize a single compressed gas cartridge for providing the propellant force for a number of different projectiles. U.S. Pat. No. 4,150,656 to CURRAN discloses such a multishot weapon utilizing compressed gas released from a compressed gas capsule to provide the propellant force. However, multishot compressed gas devices suffer from a number of problems. One problem is that the devices require relatively large and heavy gas metering mechanisms for releasing only the desired quantity of propellant gas for each shot. The multishot compressed gas capsule itself is relatively large and heavy and requires a large housing which increases the overall size of the weapon. Another problem with multishot compressed gas devices is leakage of compressed gas from the gas capsule. The gas capsules are commonly punctured to open a flow of compressed gas to the metering mechanism and pressure is often times lost due to an imperfect seal around the punctured opening. Furthermore, multishot devices generally require a propellant gas, such as CO.sub.2, that liquifies at relatively low pressures in order to provide a sufficient number of shots per gas cartridge. Although large volumes of CO.sub.2 may be stored in the liquid phase, weapons that use the liquified gas must have a bulky gas expansion chamber to convert the stored liquid into a useable gas propellant. CO.sub.2 is also a poor propellant due to its thermodynamic properties.
Other weapons which use compressed gas from a compressed or liquified gas capsule for providing ballistic propulsion force are adapted to expend the compressed material capsule in a single shot. U.S. Pat. No. 2,725,048 to KOOGLE and No. 2,660,993 to BLAKESLEE are each directed to a single shot compressed or liquified gas capsule powered device. Both of these devices used a manually actuated puncturing mechanism to puncture an opening in the compressed material capsule to release the compressed material and fire the weapon. Such manually actuated capsule puncturing mechanisms were large and bulky and again increased the overall size of the weapon. Since the user supplied the capsule puncturing force, the thickness of the capsule walls, and thus the capsule pressure was severely limited. Also, the prior single shot compressed or liquified gas capsule devices provided only a small flow area for releasing gas to propel the projectile and thus made inefficient use of the available energy. Furthermore, the manually operated mechanical puncturing devices operated relatively slowly to release the compressed gas and thus required that the weapon be held on the target for a relatively long period of time.
It is therefore an object of the invention to provide a compressed material capsule ballistic propellant device that overcomes the above-mentioned problems and others associated with prior compressed or liquified gas capsule powered devices. It is also an object of the invention to provide a method for releasing compressed material from a capsule that overcomes the problems associated with prior compressed material releasing methods.